The present application claims priority under 35 U.S.C xc2xa7 119 to Japanese Patent Application No.2000-46756, filed Feb. 18, 2000 entitled xe2x80x9cMOTION GUIDE DEVICExe2x80x9d The contents of that application are incorporated herein by reference in their entirety.
The present invention relates to a motion guide device for guiding a movable member along a predetermined track member, and more particularly, to a motion guide device capable of covering an opening for attachment formed on an upper surface of the track member by a cover covering an entire area in a width direction of the upper surface thereof.
As a device for guiding a movable member such as table of a machine tool in a predetermined direction, there is known a motion guide device constituted by mounting a movable member to a track member by means of a number of rolling members. In such device, the track member or movable member is fixed to a stationary portion of a machine, or the movable member or track member is fixed to a movable portion of the machine. The track member is formed with a plurality of bolt mounting holes for fixing the same so as to penetrate vertically the track member. However, according to a use of such guide device, there is a case where foreign bodies invade in the bolt-mounting hole and is bitten by a seal of the movable member, thus causing a trouble.
In order to solve such trouble or problem, there has been proposed a device in which a track member is entirely covered by a cover to also cover the bolt mounting holes. FIG. 5 (FIGS. 5A and 5B) shows a cover mounting structure, as one example of such device, in a motion guide device disclosed in the Japanese Patent Publication No. 2719985. In a device 1 shown in FIG. 5, a cover 3 is disposed for covering a track member 2 at an entire area in the width direction (lateral direction as viewed) of an upper surface 2a of the track member 2, undercut portions 4 are formed to both side surface portions 2a of the track member 2 at portions continuous to the upper surface 2a of the track member 2 through a round corner portions, and engaging portions 3a are formed to both the edge portions of the cover 3 to be tightly contacted to contact surfaces 4a of the undercut portions 4.
Furthermore, in the structure shown in FIG. 5, an angle xcex1 constituted by a central portion 3b of the cover 3 and the engaging portion 3a thereof is set to be smaller than an angle xcex2 constituted by the contact surface 4a of the undercut portion 4 and the upper surface 2a of the track member 2. Accordingly, at a time when the cover 3 is applied to the track member 2, if the cover 3 is forcibly pushed to the track member 2 such that the central portion 3b of the cover 3 is contacted to the upper surface 2a of the track member 2 with the engaging portion 3a of the cover 3 being engaged with the contact surface 4a of the undercut 4, the engaging portion 3a of the cover is elastically deformed so as to be opened outward, and hence, the engaging portion 3a is closely contacted to the contact surface 4a of the undercut 4 by its elastic restoring force, thus firmly holding the cover 3 on the track member 2. Further, it is noted that, in FIG. 5, although only one end side in the width direction of the track member 2 is shown, the other one end side thereof is also formed symmetrically with the mentioned one end side.
In the structure mentioned above, the engaging portion 3a gets into most inward, at its front (lower) end portion, in the width direction of the track member 2, and therefore, it is impossible to engage both the lateral pair of engaging portions 3a at the same time with the undercut portions 4.
Accordingly, the cover 3 is mounted to the track member 2 in the following manner.
First, as shown in FIG. 5B, the cover 3 is inclined (tilted) from the horizontal surface so that one engaging piece 3a is engaged with a corresponding one undercut portion 4. Under this state, the cover 3 is pulled towards the opposite side engaging portion 3a as shown with an arrow A and forcibly fitted to the upper surface of the track member 2 to thereby engage the opposite side engaging portion 3a with a corresponding undercut portion 4.
In such mounting structure, although the come-off of the cover 3 may be surely prevented, it is required to largely elastically deform the one side engaging portion 3a at the mounting time, and accordingly, this engaging portion 3a may be plastically deformed in a case when this mounting working is not well performed. Furthermore, when the cover 3 is removed, there is a case where the engaging portion 3a of the cover 3 tightly contacts the contacting surface 4a of the undercut portion 4 and the cover 3 is hence not easily peeled therefrom. In such case, it is obliged to gradually peel off (remove) the engaging portion 3a from both the longitudinal end portions of the track member 2, which requires much working time and labor for a worker, and moreover, at a time of peeling off the engaging portion 3a, there may cause an unnatural twisting force which may plastically deform the engaging portion 3a. 
An object of the present invention is to substantially eliminate defects or drawbacks encountered in the prior art mentioned above and to provide a motion guide device capable of easily mounting or dismounting (removing) a cover covering an upper surface of a track member without giving any damage to the cover during the mounting (dismounting) working time.
This and other objects can be achieved according to the present invention by providing a motion guide device comprising:
a track member having an upper surface and two side surfaces continuous to the upper surface;
a movable member mounted to the track member to be relatively movable with respect to the track member along a longitudinal direction thereof; and
a cover member covering the upper surface of the track member across an entire width direction thereof,
the track member being formed with undercut portions formed to side edge portions of the side surfaces of the track member on the upper surface side thereof, the undercuts being recessed towards a central side of the track member in the width direction thereof and
the cover member comprising a central flat portion and engaging portions formed at both end portions in the width direction thereof to be engaged with the undercut portions, respectively, so as to clamp the track member therebetween in the width direction, each of the engaging portions comprising an intermediate section to be engaged with the undercut portion of the track member and a front end section bent outward from the intermediate section so as to be opened outward in the width direction of the track member.
In the above aspect, it is to be noted that the term xe2x80x9cupperxe2x80x9d surface of the track member means a surface opposite to a lower surface in a case of providing that a mounting (mount) surface of the track member with respect to an object member is considered to be xe2x80x9clowerxe2x80x9d surface. Therefore, it is not absolute for this surface to direct the xe2x80x9cupperxe2x80x9d direction in an actual use, and in claims of the subject application, this term of xe2x80x9cupperxe2x80x9d surface is referred to as xe2x80x9chorizontalxe2x80x9d surface with reference to two side surfaces of the track member.
Furthermore, the movable member is mentioned as a member to be relatively movable with respect to the track member, and the motion guide device of the present invention is not limited to the structure in which the movable member is itself moved in use.
In a preferred embodiment of the aspect mentioned above, an outline of the intermediate section and the front end section is curved in a circular shape towards the central side of the track member in the width direction thereof. The engaging portion of the cover member has an elasticity so that both the engaging portions are simultaneously engaged with the undercut portions of the track member. That is, the cover member is formed of a plate member having an elasticity so that the central portion of the cover member is engaged with the upper surface of the track member and both the engaging portions of the cover member are simultaneously engaged with the undercut portions of the track member by depressing the flat portion of the cover member to the upper surface of the track member.
The cover member has a longitudinal dimension substantially equal to that of the track member.
The upper surface and the side surfaces of the track member are continuous to each other through round portions and each of the engaging portions of the cover member further comprises a base section curved outward from the intermediate section so as to coincide in shape with the round portion of the track member.
The track member is formed with openings to the upper surface thereof.
According to the present invention of the structures mentioned above, the front end sections of the engaging portions of the cover member are opened outward from the intermediate portions thereof, so that, by placing the engaging portions to the end edges of the upper surface of the track member and then pushing the cover member towards the upper surface of the track member, the engaging portions are elastically deformed outward and slid over the continuous round portion connecting the upper surface of the track member and the side surfaces thereof and the intermediate sections of the engaging portions are engaged with the recessed undercut portions of the track member. On the other hand, when the cover member is removed from the track member, the outward opened front end sections of the engaging portions are grasped and pulled upward, thus being easily removed. Since such working can be done without applying a large force locally, the cover member cannot be deformed.
The circularly curved shape of the intermediate section and the front end sections of the engaging portions can allow the engaging portions to be easily elastically deformed at the time of being attached to or removed from the track member and the working efficiency can be improved. The deformation of the cover member can be also prevented.
The cover member can be easily fitted to the track member by simultaneously fitting the engaging portions to the undercut portions of the track member.
The nature and further characteristic features of the present invention will be made more clear from the following descriptions made with reference the accompanying drawings.